This research aims to investigate the influence of alveolar ridge preservation, after extraction of maxillary posterior teeth, on the potential need of sinus floor augmentation procedures (that include lateral or crestal sinus augmentations). From peri-apical radiographs, maxillary posterior teeth will be divided into 4 groups according to the relationship of their apexes with the sinus. Then, the patients will be divided into 2 sub-groups: unassisted socket healing (only extraction) and ARP group (extraction + ARP) and their CBCT scans before implant placement will be collected. The CBCT scans should be at least 4 months post-extraction and ARP. Depending on the residual bone height, patients will be divided into 3 categories, according to the ABC classification:

1. In need of lateral sinus floor augmentation
2. In need of crestal sinus floor augmentation
3. No need for sinus floor augmentation, therefore, implant placement.

These divisions will be conducted, according to:

- The residual bone height (RBH) which is the height in mm from the alveolar ridge crest to the lowest point of the maxillary sinus floor.

The results of the proposed hypothesis are verified and interpreted after statistical analysis.

1. Department or division:

   Department of Periodontology, Faculty of Dental Medicine, Saint Joseph University of Beirut, Beirut, Lebanon.

2. Type of the project:

   Master's Thesis in Periodontology.

3. Title of the project:

   Impact of Alveolar Ridge Preservation on the Potential Need for Sinus Floor Elevation in Posterior Maxillary Implant Sites: A 10-year Retrospective Radiographical Study.

4. Research and publication team

   • Principle researcher:

   Nadine Chamas, DDS, Department of Periodontology, Faculty of Dental Medicine, Saint Joseph University of Beirut, Beirut, Lebanon. nadine.chamas@net.usj.edu.lb

   • Data and manuscript revision Abdel Rahman Kassir, DDS, MSc, Department of Periodontology, Faculty of Dental Medicine, Saint Joseph University of Beirut, Beirut, Lebanon. Abdel.kassir@hotmail.com
   • Data analyst:

   Joe Khoury, DDS, MSc, Department of Periodontology, Faculty of Dental Medicine, Saint Joseph University of Beirut, Beirut, Lebanon. Joekhoury.perio@gmail.com

   • Data analyst and manuscript revision:

   Joseph Ryan Younes, DDS, Department of Periodontology, Faculty of Dental Medicine, Saint Joseph University of Beirut, Beirut, Lebanon. joryanyounes@gmail.com

   • Director of the project: Nadim Mokbel, DDS, MSc, PhD, Department of Periodontology, Faculty of Dental Medicine, Saint Joseph University of Beirut, Beirut, Lebanon. nadim.mokbel@gmail.com

   Contributor roles in publication:

   • Nadine Chamas, DDS: conceptualization of the project, handling of the measurements to be conducted, data preservation and manuscript writing.
   • Abdel Rahman Kassir, DDS, MSc: Data revision and manuscript proof reading.
   • Joe Khoury (El), DDS, MSc: Data analysis and manuscript revision.
   • Joseph Ryan Younes, DDS: Data collection, data analysis and manuscript revision.
   • Nadim Mokbel, DDS, MSc, PhD: conceptualization and administration of the project, data supervision and manuscript revision.

5. Type of the study:

   Retrospective observational study.

6. Budget

   Self-funded.

7. Key words:

Alveolar Bone Loss, Alveolar Process Atrophy, Extraction, Tooth Socket, Sinus Floor Augmentation.

8. General context of the study

Following tooth extraction, the alveolar bone undergoes a remodeling process that causes structural and dimensional modifications. A resorption of the ridge is observed 6 months following tooth extraction, with a reduction of 11-22% and 29-63% in the vertical and horizontal dimensions, respectively, with two thirds of this resorption occurring within the first 3 months (2). A significantly larger ridge reduction was observed in the molar region than in the anterior region by Araujo et al (1). In the posterior area, the residual ridge dimensions following tooth extraction are thought to result from two biological processes: the resorption of the alveolar bone, as well as the pneumatization of the maxillary sinus (3).

Maxillary sinus pneumatization is a physiological process characterized by the expansion of the sinus over time, and it accounts for up to 46% of the variation in ridge height following tooth extraction (3). This process has been attributed to the decrease of functional forces transferred to the bone after tooth loss, causing a shift in the remodeling process towards a resorptive pattern (3). This particular type of disuse atrophy occurs according to Wolff's law and is enhanced by the presence of a positive air pressure into the sinus cavity (4). A greater risk of developing sinus pneumatization has been associated with extraction of molars compared to premolars, second molars compared to first molars, multiple extractions of adjacent teeth and extraction of teeth with roots protruding into the sinus cavity (3).

The combined result of alveolar bone resorption and sinus pneumatization can lead to a significant reduction in ridge dimensions, which can make implant placement challenging in the posterior sector (2). Consequently, additional surgical procedures may be needed to increase the vertical and horizontal dimension of the alveolar ridge, such as transalveolar or lateral sinus floor elevation (SFE) combined or not with guided bone regeneration.

The selection of SFE technique depends critically on the residual bone height (RBH) and sinus anatomy, where transalveolar or crestal sinus lift is usually recommended when the RBH is ≥5mm, whereas a lateral window sinus lift is recommended when the bone height is <5mm (3).

However, all these procedures are linked with a significant rate of complications, increased patient morbidity, high cost and an extended course of therapy (4). Therefore, alveolar ridge preservation (ARP) was developed and can be employed as a valid treatment modality in the posterior maxilla, as it can significantly reduce post-extraction ridge dimensional alterations (3). Various types of biomaterials have been utilized for alveolar ridge preservation, including xenografts that were reported to show consistent results in minimizing the extent of alveolar bone resorption and dimensional ridge changes (3).

Alveolar ridge preservation has been demonstrated to improve the profile of ridges as compared to non-grafted sites and previous systematic reviews have shown evidence supporting its success (2). However, the treatment could neither completely prevent volume nor contour alteration. Therefore, the aim of this retrospective study is to investigate the influence of alveolar ridge preservation using xenografts after extraction of posterior maxillary teeth on the need for sinus floor augmentation compared to unassisted socket healing.

9. Summary description of the subject and approach

This research aims to investigate the influence of alveolar ridge preservation, after extraction of maxillary posterior teeth, on the potential need of sinus floor augmentation procedures (that include lateral or crestal sinus augmentations). From peri-apical radiographs, maxillary posterior teeth will be divided into 4 groups according to the relationship of their apexes with the sinus. Then, the patients will be divided into 2 sub-groups: unassisted socket healing (only extraction) and ARP group (extraction + ARP) and their CBCT scans before implant placement will be collected. The CBCT scans should be at least 4 months post-extraction and ARP. Depending on the residual bone height, patients will be divided into 3 categories, according to the ABC classification:

1. In need of lateral sinus floor augmentation
2. In need of crestal sinus floor augmentation
3. No need for sinus floor augmentation, therefore, implant placement.

These divisions will be conducted, according to:

- The residual bone height (RBH) which is the height in mm from the alveolar ridge crest to the lowest point of the maxillary sinus floor.

The results of the proposed hypothesis are verified and interpreted after statistical analysis.

10. Innovative aspect of the study

This retrospective study aims to identify, from the large data of alveolar ridge preservation procedures performed in maxillary posterior teeth, the potential need for sinus floor augmentation procedures before implant placement. In other words, based on the final residual bone height, between 4 and 12 months after dental extraction with or without alveolar ridge preservation, the potential need will be calculated for three possible clinical scenarios: lateral sinus floor augmentation, crestal sinus elevation or no need for sinus floor elevation therefore simple implant placement.

11. Objective of the study

• Primary objective: This retrospective analysis aims to investigate the effects of alveolar ridge preservation on mid-ridge height between 4 and 12 months after tooth extraction.

• Secondary objective: To assess the potential need for either lateral sinus elevation or crestal sinus elevation following tooth extraction and alveolar ridge preservation in the posterior maxilla.

  12. Hypothesis

• Null hypothesis H0:

Alveolar ridge preservation in posterior maxillary teeth doesn't influence the need for lateral sinus floor augmentation.

• Alternative hypothesis H1:

Alveolar ridge preservation in posterior maxillary teeth reduces the need for lateral sinus floor augmentation.

13. Methodology 13.1. Employed techniques.

• Peri-apical radiographs will be collected of all patients having underwent extraction of maxillary posterior teeth with and without alveolar ridge preservation (test and control group), from January 2016 till January 2026.

• Images will be selected considering a high-level technical standard (i.e. appropriate sharpness, density and contrast), clearly showing the maxillary posterior teeth apices and the sinuses floor.

• An assessment of the topographic relationship of each root to the maxillary sinus floor will be conducted and posterior teeth will be classified into the following categories, regarding the two-dimensional relationship of the apexes with the maxillary sinus floor (MSF), based on the Jung et al. classification in 2009 (6):

  o Type 1: the maxillary sinus floor is located above the root tip(s).

  • Type 2: the root apex touches the sinus floor.
  • Type 3: the MSF is interposed between the roots.

• Mid-ridge height (in mm) at selected points will be measured on CBCT scans of patients who underwent alveolar ridge preservation or not, with CBCT scans being taken between 4-12 months later. Depending on the final residual bone height (RBH), patients will be allocated to one of three categories before implant placement. This is according to the ABC sinus classification.

  a) RBH <5mm: need of external sinus floor augmentation. b) RBH = 6-9mm: need for crestal sinus floor augmentation. c) RBH >10mm: no need for sinus elevation procedures and simple implant placement.

• One operator will conduct all the measures as well as the data collection. An intra-examiner calibration will be conducted by repeating the measurements by the same operator.

• The data collected will be quantitative and qualitative.

13.2. Population

Inclusion criteria:

• Patients aged ≥18 years.
• Patients who underwent alveolar ridge preservation after extraction of maxillary posterior teeth, as a test group.
• Patients who underwent extraction of maxillary posterior teeth with unassisted socket healing without alveolar ridge preservation as a control group.

Exclusion criteria

• The presence of a clinically symptomatic periapical radiolucency, acute abscesses, or chronic sinus tract, that may falsify the classification of posterior maxillary teeth on 2D radiographs.

Number of subjects needed: 130; total 8 groups).

13.3. Description of the variables

Primary outcome variable: Mid-ridge height measured from the ridge to the maxillary sinus floor (quantitative).

Secondary outcome variable: need for external sinus lift, crestal sinus lift or no need (qualitative variable).

Source of the variables: On peri-apical radiographs, mid-ridge height will be measured in mm from the sinus floor to the ridge. Then, on CBCT scans the same mid-ridge height will be calculated at the future ideal implant site.

13.4. Employed statistical methods.

• Sample size calculation: For a multiple linear regression with level of significance of 5%, power of 95%, medium effect size (0.15) and 4 predictors (relationship with maxillary sinus floor, ARP/no ARP, …), the total sample size needed is 130.

• Statistical analysis: Descriptive statistics will be presented as means ± standard deviations for continuous variables and proportions for categorical variables.

We will test for the normal distribution of the outcome using the Shapiro-Wilk and Kolmogorov-Smirnov tests.

The association between the primary outcome (difference in mid-ridge height) measured in mm and other variables will be assessed using independent t-test.

The effect of the relationship with MSF and whether ARP was performed or not on the difference in mid-ridge height will be assessed by performing a multiple logistic regression to account for the effect of other variables.

For the secondary outcomes, based on the residual bone height, the teeth in each group will be classified in three categories: lateral sinus lift, crestal sinus lift or no need for sinus lift elevation, which will be reported as proportions.

The G*Power software 3.1.9.7 (Heinrich Heine Universität Düsseldorf, Germany) will be used to calculate the minimum required sample size, ensuring a sufficiently powered study. Since there is no specific literature reporting effect sizes used in similar studies, we will be adopting a medium effect size of 0.15.

The relationship with the maxillary sinus floor will be categorized into 4 groups (type 0, type 1, type 2 and type 3), therefore creating a 4-level variable. The presence/absence of ARP variable will have 2 levels: ARP and no ARP. Therefore, we will need to consider the inclusion of 4 predictors in the regression model (3 for the 4-level variable and 1 for the 2-level variable).

Therefore, for a multiple linear regression with a medium effect size (f2 = 0.15), a level of significance α of 0.05 (5%), power of 0.95 (95%) and the inclusion of 4 predictors, the total sample size needed is 130.

14. Strong points

Clinical relevance of the study: This study will provide clinicians with a percentage of final need for lateral or crestal sinus floor elevation procedures after alveolar ridge preservation, based on the initial relationship of the root apexes of posterior maxillary teeth before extraction. Therefore, facing a clinical situation where a posterior maxillary molar needs extraction, the clinician will be able to know approximately, after classifying the molar into one of the 4 categories, the prognosis of the case.

15. Awaited scientific productions. Publication in a scientific journal.

16. Study design

17. Calendar

Starting date: after the protocol acceptance in November 2025 Ending date: April 2026

18. References

1. Araújo MG, Silva CO, Misawa M, Sukekava F. Alveolar socket healing: what can we learn?. Periodontology 2000. 2015 Jun;68(1):122-34.
2. Khoury EJ, Sagheb K, Al-Nawas B, König J, Schiegnitz E. Does alveolar ridge preservation reduce the need for sinus floor elevation: A comparative study to spontaneous healing. Clinical Implant Dentistry and Related Research. 2024 Dec;26(6):1325-37.
3. Lam L, Ivanovski S, Lee RS. Alveolar ridge preservation in posterior maxillary teeth for reduction in the potential need for sinus floor elevation procedures: A pilot study. Clinical oral implants research. 2024 Dec;35(12):1568-84.
4. Lombardi T, Bernardello F, Berton F, Porrelli D, Rapani A, Camurri Piloni A, Fiorillo L, Di Lenarda R, Stacchi C. Efficacy of alveolar ridge preservation after maxillary molar extraction in reducing crestal bone resorption and sinus pneumatization: A multicenter prospective case-control study. BioMed research international. 2018;2018(1):9352130.
5. Wang HL, Katranji A. ABC sinus augmentation classification. International Journal of Periodontics & Restorative Dentistry. 2008 Aug 1;28(4).
6. Jung YH, Cho BH. Comparison of panoramic radiography and cone beam computed tomography for assessing the relationship between the maxillary sinus floor and maxillary molars. Imaging Science in Dentistry. 2009;39(2):69-73.

Inclusion Criteria:

• • Patients aged ≥18 years.

  • Patients who underwent alveolar ridge preservation after extraction of maxillary posterior teeth, as a test group.
  • Patients who underwent extraction of maxillary posterior teeth with unassisted socket healing without alveolar ridge preservation as a control group.

Exclusion Criteria:

• • The presence of a clinically symptomatic periapical radiolucency, acute abscesses, or chronic sinus tract, that may falsify the classification of posterior maxillary teeth on 2D radiographs.

Patients who underwent extraction of posterior maxillary molars at the Saint Joseph University of Beirut's dental center, having underwent alveolar ridge preservation or not.